The present application relates to a battery storage system that stores electrical power, which is obtained by a natural energy converting apparatus, for example, a photovoltaic power generation module, in a battery storage cell and converts electrical power to be supplied to a load, and to a controlling method of the same.
In recent years, battery storage systems each combining a plurality of power supplies such as a photovoltaic cell, a battery storage cell, and a commercial power system have prevailed more and more. This battery storage system includes a power converter that generates, from an output voltage of the photovoltaic cell, electrical power to be supplied to a load and further electrical power for charging the battery storage cell, a control circuit that controls this power converter, and the like.
In such a battery storage system, for constantly stably operating the control circuit, it is important how to ensure an operating power supply of the control circuit in the case of power failure of the commercial power system, for example.
For example, Japanese Patent Application Laid-open No. 2008-054473 (paragraphs 0023-0031) discloses one that enables necessary electrical power to be supplied from any of a photovoltaic cell, a battery storage cell, and a commercial power system to a control unit. Specifically, in the case of power failure of the commercial power system, the electrical power is supplied from the photovoltaic cell or the battery storage cell and, when the battery storage cell reaches a discharge lower limit, the electrical power is supplied from the photovoltaic cell or the commercial power system. With this, it is possible to keep the stable operation of the control unit.
Note that, regarding selection from among the outputs of the photovoltaic cell, the battery storage cell, and the commercial power system, the following methods are disclosed, for example. As one of the methods, output voltages are compared with one another and the output of the power supply that can provide a highest output voltage is selected. As another method, the output of the power supply that can provide an output voltage larger than a predetermined set value is selected.